openmpi/ompi/mca/btl/openib/help-mpi-btl-openib.txt

# -*- text -*-
#
# Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
#                         University Research and Technology
#                         Corporation.  All rights reserved.
# Copyright (c) 2004-2005 The University of Tennessee and The University
#                         of Tennessee Research Foundation.  All rights
#                         reserved.
# Copyright (c) 2004-2005 High Performance Computing Center Stuttgart, 
#                         University of Stuttgart.  All rights reserved.
# Copyright (c) 2004-2006 The Regents of the University of California.
#                         All rights reserved.
# $COPYRIGHT$
# 
# Additional copyrights may follow
# 
# $HEADER$
#
# This is the US/English general help file for Open MPI.
#
[btl_openib:retry-exceeded]
The InfiniBand retry count between two MPI processes has been
exceeded.  "Retry count" is defined in the InfiniBand spec 1.2
(section 12.7.38):

    The total number of times that the sender wishes the receiver to
    retry timeout, packet sequence, etc. errors before posting a
    completion error.

This error typically means that there is something awry within the
InfiniBand fabric itself.  You should note the hosts on which this
error has occurred; it has been observed that rebooting or removing a
particular host from the job can sometimes resolve this issue.  

Two MCA parameters can be used to control Open MPI's behavior with
respect to the retry count:

* btl_openib_ib_retry_count - The number of times the sender will
  attempt to retry (defaulted to 7, the maximum value).

* btl_openib_ib_timeout - The local ACK timeout parameter (defaulted
  to 10).  The actual timeout value used is calculated as:

     4.096 microseconds * (2^btl_openib_ib_timeout)

  See the InfiniBand spec 1.2 (section 12.7.34) for more details.